This application is based on and claims priority to Japanese Patent Application No. 2001-301620, filed Sep. 28, 2001 the entire contents of which is hereby expressly incorporated by reference.
1. Field of the Invention
The present invention relates to oil injection lubrication for engines and more particularly to oil injection systems and methods for lubricating a two-cycle engine.
2. Description of the Related Art
In two-cycle engines, it is a common practice to mix lubricating oil with induction air to lubricate engine parts. Typically, the intake air is pre-compressed inside a crank chamber before being sent into the cylinders. In this type of two-cycle engine, oil is guided to an intake passage and further into the engine by the intake air. More specifically, the oil encounters the intake air inside the intake passage and is misted therein. The misted oil is then drawn into the crank chamber as the piston ascends and a valve opens to allow intake air to enter the crank chamber. The misted oil lubricates rotating parts in and around the crankshaft and within the interior wall of the cylinder.
In conventional two-cycle engines, fuel mixes with the intake air inside the intake passageway to reduce the viscosity of the oil which promotes misting of the oil. However, in direct injection-type two-cycle engines in which the fuel is directly sprayed into the combustion chamber, the viscosity of the oil drawn into the crank chamber is not reduced by dilution with the fuel. The undiluted liquid oil is, therefore, more difficult to convert into a mist. Since the oil may not be sufficiently misted in the intake air, the amount of oil supplied to the engine may be reduced. Insufficiently misted oil results in liquid oil depositing onto the interior wall surface inside the intake passageway. More liquid oil deposits on the wall surfaces of the intake passageway when the flow of intake air decreases, such as during low speed operation.
One aspect of the present invention includes the realization that the rotation of the crankshaft of an internal combustion engine can be used to redistribute oil that has condensed in the crankcase chamber. For example, a lubricant recess can be preferably located adjacent, and generally below, a throw of a vertically-oriented crankshaft, such that a connecting rod endcap attached to the crankshaft throw passes over the recess during at least a portion of its rotational travel. The endcap is preferably configured with radial oil holes to help establish a flow path caused by a pressure differential due to rotation of the crankshaft. In at least one embodiment, the pressure differential is sufficient to draw oil from the recess into the endcap and throw the oil about the crankcase chamber.
According to another aspect of the present invention, a lubrication system for a two-cycle engine is provided. The engine, which may be of the direct fuel injection type, has a vertical crankshaft and a lubrication recess disposed generally adjacent to a throw of the crankshaft. The lubrication recess opens upwardly such that at least a portion of a connecting rod endcap passes over the recess.
The lubrication recess is preferably formed in an interior wall of the engine crankcase. Liquid oil may be directed to the lubrication recess by a guide groove that extends from an air intake of the crankcase to the lubrication recess.
The endcap preferably has one or more holes formed therethrough and providing an opening in an interior surface of the endcap and an opening in the exterior surface of the endcap. As the crankshaft rotates, the opening in the interior surface of the endcap preferably passes over the lubrication recess during a predetermined range of crankshaft rotation.
According to another aspect, a two-stroke engine has one or more cylinders with each cylinder having a piston, a vertical crankshaft, and a connecting rod that connects the piston to a throw of the crankshaft. The connecting rod has an endcap that allows it to connect to the crankshaft throw, the endcap having one or more oil holes formed therethrough thus providing fluid communication between an opening in an interior peripheral surface and an opening in an exterior peripheral surface of the endcap. A lubrication recess is formed adjacent the crankshaft and generally below a crankshaft throw. As the crankshaft rotates, each opening in the interior peripheral surface of the endcap to pass over the lubrication recess.
The crankshaft rotation can cause a pressure differential between the interior and exterior surfaces of the endcap sufficient to draw oil from within the lubrication recess upwardly and into the interior peripheral surface opening. The oil is then thrown through the exterior peripheral surface opening.
Another aspect of the present invention is directed to an outboard motor having a powerhead, a driveshaft housing depending from the powerhead, and a lower unit connect to and disposed below the driveshaft housing. The powerhead includes an internal combustion engine coupled to a propeller of the lower unit through a driveshaft extending through the driveshaft housing for propelling a watercraft. The internal combustion engine further has a cylinder block defining a cylinder bore and a cylinder head connected to the cylinder block. The cylinder head has a recess in one of its surfaces which cooperates with a piston surface and the cylinder bore to define a combustion chamber.
A vertical crankshaft is configured for rotation within a crankcase chamber formed, in part, by a crankcase member, and is coupled to the piston through a connecting rod that has a large end engaging the crankshaft and a small end engaging the piston. The crankcase member further defines an air intake passageway having an air and oil regulating valve disposed therein.
A lubrication recess is formed by the crankcase member and is disposed generally below the large end of the connecting rod during at least a range of the crankshaft rotation. The crankcase member further defines a guide groove configured to urge deposited lubricant to flow toward the lubricant recess.
The large end of the connecting rod draws lubricant from the lubricant recess and throws the lubricant within the crankcase chamber.
According to yet another aspect, a two-stroke internal combustion engine includes one or more cylinders and a piston for reciprocating within each cylinder. A connecting rod is rotatably coupled to each piston and is further coupled to a throw of a vertical crankshaft by an endcap. The crankshaft and connecting rod are disposed within a crankcase chamber.
One or more oil holes are formed radially through the endcap thereby providing fluid communication between a first opening disposed inwardly from an outer peripheral surface and a second opening in the outer peripheral surface of the endcap.
A lubrication recess can be disposed adjacent the crankshaft and generally below a throw of the crankshaft during at least a range of its rotation. Rotation of the crankshaft may cause lubricant from within the lubrication recess to be drawn into the first opening and discharged out of the second opening. Rotation of the crankshaft can cause a pressure differential sufficient to draw lubricant into the first opening. The lubricant can further be used to lubricate the coupling between the connecting rod and the throw of the crankshaft.
The crankshaft rotation can additionally or alternatively cause the endcap to splash the lubricant within the lubrication recess thereby forcing lubricant into the first opening.
A guide groove may be provided in a lower surface of the crankcase and extend generally from an air intake of the crankcase to the lubrication recess.
According to another aspect, a two-stroke internal combustion engine has one or more cylinder each having a piston for reciprocation therein. Each piston is rotatably coupled to a connecting rod which is, in turn, coupled to a throw of a crankshaft by an endcap. The crankshaft is disposed generally vertically within a crankcase chamber of the engine. A lubrication recess is disposed adjacent to the crankshaft and generally below a throw of the crankshaft.
Liquid oil within the crankcase chamber may collect within the lubrication recess, after which the endcap and/or connecting rod can throw the collected oil about the crankcase chamber.
According to yet another aspect, an outboard motor has an internal combustion engine with a crankshaft journaled for rotation within a crankcase and couple to a driveshaft for rotating a propeller connect to the driveshaft. The internal combustion engine includes means for causing oil to pool adjacent a throw of the crankshaft and means for redistributing pooled oil around the crankcase.